[Py OV] Unify system path handling in Python API

[almilosz]

Details:

• Remove convert_path_to_string() in favour of to_fs_path(). Use to_fs_path() consistently across the codebase.
• Add support for pathlib.Path to Core::add_extension and FrontEndManager::register_front_end. Add tests
• Unicode character support in FrontEnd::load() and FrontEnd::supported() is tested e.g. in test_onnx.py::TestUnicodePathsONNX pr24801. Replace the usage of Common::utils::convert_path_to_string() and the extra Windows-specific fix with the Common::utils::to_fs_path().
• Pass enable_mmap parameter to FrontEnd::load(). It was previously omitted in a #if defined block.
• After switching pyopenvino's FrontEnd.add_extenstion to use to_fs_path, the test test_frontend_onnx.py::test_add_extension_unicode_paths failed with the error:
  "No mapping for the Unicode character exists".
  This issue was resolved by using .native() in the C++ implementation of FrontEnd::add_extension()
• cache_model_path, read_tensor_data, FileDescriptor, validate_path – not exposed in Python API

Tickets:

• CVS-179150

[Copilot]

Pull request overview

This PR introduces improved path handling in the OpenVINO Python API to support pathlib.Path and bytes types in addition to strings. The implementation adds a new to_fs_path() helper function that converts Python path objects to std::filesystem::path, which properly handles Unicode paths across platforms.

Changes:

• Added to_fs_path() helper to convert Python path objects (str, bytes, pathlib.Path) to std::filesystem::path
• Updated Core::compile_model, Core::read_model, and Core::add_extension to use the new path handling
• Updated FrontEndManager::register_front_end and FrontEnd::add_extension to accept flexible path types
• Updated documentation to reflect support for Union[str, bytes, pathlib.Path] where applicable

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
src/bindings/python/src/pyopenvino/graph/node_factory.cpp	NodeFactory::add_extension has new to_fs_path() code commented out; still using old approach
src/bindings/python/src/pyopenvino/frontend/manager.cpp	FrontEndManager::register_front_end successfully migrated to to_fs_path(); load_by_model has new code commented out
src/bindings/python/src/pyopenvino/frontend/frontend.cpp	FrontEnd::add_extension migrated to to_fs_path(); load and supported methods have new code commented out
src/bindings/python/src/pyopenvino/core/core.cpp	Core::compile_model, read_model, and add_extension successfully migrated to to_fs_path() with minor issues

Comments suppressed due to low confidence (2)

src/bindings/python/src/pyopenvino/frontend/frontend.cpp:52

• The commented-out code using to_fs_path() should be uncommented and used to replace the manual string conversion and Windows-specific wstring handling. The std::filesystem::path type with pybind11's automatic conversion already handles Unicode paths correctly across platforms, including Windows. The current manual conversion and conditional wstring usage adds unnecessary complexity.

However, note that the current code has special handling for bytes inputs (line 52) where it passes enable_mmap as a second parameter to a different overload. If this is intentional behavior that should be preserved, the logic would need to be restructured to use to_fs_path() while still handling this case.

                // return self.load(Common::utils::to_fs_path(py_obj));

                // check if model path is either a string/pathlib.Path/bytes
                std::string model_path = Common::utils::convert_path_to_string(py_obj);
                if (py::isinstance(py_obj, py::module_::import("pathlib").attr("Path")) ||
                    py::isinstance<py::str>(py_obj)) {

                // Fix unicode path
#if defined(OPENVINO_ENABLE_UNICODE_PATH_SUPPORT) && defined(_WIN32)
                    return self.load(ov::util::string_to_wstring(model_path.c_str()));
#else
                    return self.load(model_path.c_str());
#endif
                }
                return self.load(model_path, enable_mmap);

src/bindings/python/src/pyopenvino/frontend/frontend.cpp:95

• The commented-out code using to_fs_path() should be uncommented and used to replace the manual string conversion and Windows-specific wstring handling. The std::filesystem::path type with pybind11's automatic conversion already handles Unicode paths correctly across platforms, including Windows. The current manual conversion and conditional wstring usage adds unnecessary complexity and is inconsistent with the approach used elsewhere in this PR.

                // return self.supported(Common::utils::to_fs_path(model));

                // check if model path is either a string/pathlib.Path/bytes
                std::string model_path = Common::utils::convert_path_to_string(model);
                if (py::isinstance(model, py::module_::import("pathlib").attr("Path")) ||
                    py::isinstance<py::str>(model)) {

                // Fix unicode path
#if defined(OPENVINO_ENABLE_UNICODE_PATH_SUPPORT) && defined(_WIN32)
                    return self.supported(ov::util::string_to_wstring(model_path.c_str()));
#else
                    return self.supported(model_path.c_str());
#endif
                }

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

[p-wysocki]

Discussed offline, LGTM

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

src/bindings/python/src/pyopenvino/core/core.cpp:687

• Core.add_extension(library_path) is now bound to std::filesystem::path, but the docstring still states :type library_path: str. Since the binding will accept pathlib.Path (and likely bytes via the filesystem caster), please update the documented type to match the actual accepted inputs (e.g., Union[str, bytes, pathlib.Path]).

    cls.def("add_extension",
            static_cast<void (ov::Core::*)(const std::filesystem::path&)>(&ov::Core::add_extension),
            py::arg("library_path"),
            R"(
                Registers an extension to a Core object.

                :param library_path: Path to library with ov::Extension
                :type library_path: str
            )");